To improve the dosage of Vincristine (VCR) in cancer patients who can presently only receive a maximum dose of 2 mg irrespective of body size, a study of vincristine pharmacokinetics/pharmacology and neurotoxicity was initiated. A liquid chromatographic assay with electrochemical (LC-EC) detection was developed for quantitation of vincristine in plasma of patients receiving doses of up to 2 mg of the drug. Detection and quantitation of vincristine with this method has been acheived using daunorubicin (DNR) as internal standard. On this system the retention times for VCR and DNR were 11.8 and 6.4 minutes respectively. A limit of detection of 0.5 ng/ml was established for VCR in plasma with a linear calibration in the range of 2.5 - 125 ng/ml. Characterisation of VCR disposition in a 69.7 kg female patient who received a dose of 0.9 mg of the drug is currently in progress.